add NewRasterDirect for creating a canvas drawing to pre-allocated pixels

R=reed@google.com
TBR=scroggo@google.com

Author: reed@chromium.org

Review URL: https://codereview.chromium.org/196923004

git-svn-id: http://skia.googlecode.com/svn/trunk@13824 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed